How music festivals have replaced seaside holidays

There are photographs, taken during the 1930s and 40s, of British seaside towns teeming with people. Absolutely ram-a-jam, chock-full: hundreds of holidaying workers walking arm in arm along promenades, giggling as they lean over railings, perching atop one another's knees on beaches so pebbly that every deckchair looks as though it's about to snap shut and swallow them.

Where did they go, those people? Why did they abandon Blackpool and Skegness and Margate and Rye? The usual line is that, some time in the 70s, the holidaying Brits discovered the package tour and departed en masse to southern Spain and Florida and, now, to Dubai. That's true. But an awful lot of their children decided to go to festivals.

Over the past decade, festivals have become more and more like old-fashioned holidays. You book upfront. You take your mates, or your family, as you prefer. You camp if you're poor or you B&B if you're not. You make an entire week out of what used to be a long weekend: rocking up to site on Wednesday night, leaving late Monday, so you've got Tuesday to recover before you're back to work the next day. Like those ancient seaside jaunts, festivals are properly communal experiences. Like campsites or Butlins or end-of-the-pier shows, festivals are nothing without you and everyone else, all those similarly fun-seeking strangers that you end up having a laugh with, dancing with, running away with, running away from. All laughs are a zillion times more hilarious when you're surrounded by strangers.

The music business would have you believe that festivals are about who's playing: U2, Beyoncé, the Cure, the National, Rastamouse. And they are, for the music business. Playing live is how most bands make their money and the biggest earn a fortune during the festival season. But for us punters, the headliners are a minor part of the appeal. I know of a teenager who informed her parents that she was going to Reading this year. When they said: "Why, who's playing?", she didn't know. She wants to go, not because of My Chemical Romance. Not because of Pulp. Not even because of a Reading crowd's long-term dedication to the idea that it's entertaining to burn bin-bags of an evening. But because everyone else is going.

Hanging out with a group of like-minded people is the stuff of life, but these days, your friends aren't enough. Everyone's searching for a crowd. Not only virtually – how many lonely evenings have been saved by Facebook or Twitter? – but offline too. As society becomes more atomised, as we live more singly, there's something thrilling about hanging out in a big group, whether that's at a football match, a royal wedding or crammed in a small urban space surrounded by policemen who won't let you out to have a wee. It's all about the throng, the swarm, the get-together. Mobile phone companies build campaigns around flash-mobs. The BBC spends our licence fee on Radio 1's Big Weekend and the Proms (good things).

There are now so many festivals that you could spend your whole summer bouncing from one to another, whether you fancy communing with people who are into books, comedy, music or watching military aircraft fly by in choreographed patterns. I actually don't know anyone over 18 who hasn't been to a festival in their time. It's what we do now, as a nation. It's how we relax.

You know how your gran says: "We made our own fun back then?" We still do. The celebrity entertainment might be what gets the column inches, but it's pretty irrelevant to your good time. Even the weather doesn't matter that much. It's the crowd that makes the fun. A mass of people all doing much the same thing will start acting as one entity very quickly. Like Twitter, with its hashtags and quick-to-conform opinion, a crowd knows what it thinks. If a band is boring, the crowd lets them know: drifts away, or doesn't respond, or starts singing something else. If, however, a band – or a speaker, or a comedian, or an actor – does what the audience wants, then the atmosphere at a festival is second to none.

Which leaves the photos. We need a documentary snapper to start taking proper pictures. Of parades of spacemen at Bestival. Of befuddled hordes on the train-track to Lost Vagueness. Polite Hay-goers queuing for Alexander McCall Smith. Head-phoned ravers at a silent club tent. Someone should document them properly, take festivals seriously as the UK's chosen form of recreation.

Because, in the future, when we holiday in a different way – all staying at home and Skyping in sync? – such photos will seem as heartbreaking, as optimistic and quaint as those pictures of packed piers and seaside treats.